The objectives of this project is to study the biochemical interactions of kallikrein with its substrates and inhibitors, the role of HMW kininogen in plasma proteolysis, the interaction of the contact system with platelets and measurement of the kinin forming system in human disease. Accomplishments this year include studies of the activation of plasma kallikrein in hyperbetalipoproteinemia and typhoid fever, observations on Hageman factor induced fibrinolysis in Bechet's disease, localization and purification of platelet alpha1-antitrypsin, development of a rapid high yield purification of prekallikrein, study of the function and immunochemistry of prekallikrein-high molecular weight kininogen complex in plasma and investigation of proteins which potentiate Hageman factor fragments other than HMW kininogen.